Computational Insights into Schottky Barrier Heights: Graphene and Borophene Interfaces with H- and H́-XSi₂N₄ (X = Mo, W) Monolayers

The two-dimensional (2D) semiconducting family of XSi₂N₄ (X = Mo and W), an emergent class of air-stable monolayers, has recently gained attention due to its distinctive structural, mechanical, transport, and optical properties. However, the electrical contact between XSi₂N₄ and metals remains a mystery. In this study, we inspect the electronic and transport properties, specifically the Schottky barrier height (SBH) and tunneling probability, of XSi₂N₄-based van der Waals contacts by means of first-principles calculations. Our findings reveal that the electrical contacts of XSi₂N₄ with metals can serve as the foundation for nanoelectronic devices with ultralow SBHs. We further analyzed the tunneling probability of different metal contacts with XSi₂N₄. We found that the H-phase XSi₂N₄/metal contact shows superior tunneling probability compared to that of H́-based metal contacts. Our results suggest that heterostructures at interfaces can potentially enable efficient tunneling barrier modulation in metal contacts, particularly in the case of MoSi₂N₄/borophene compared to MoSi₂N₄/graphene and WSi₂N₄/graphene in transport-efficient electronic devices. Among the studied heterostructures, tunneling efficiency is highest at the H and H́-MoSi₂N₄/borophene interfaces, with barrier heights of 2.1 and 1.52 eV, respectively, and barrier widths of 1.04 and 0.8 Å. Furthermore, the tunneling probability for these interfaces was identified to be 21.3 and 36.4%, indicating a good efficiency of carrier injection. Thus, our study highlights the potential of MoSi₂N₄/borophene contact in designing power-efficient Ohmic devices.